'Considerable' rating

Hm. Is it bothersome that the lowland weather forecast is, through most of the winter, "mostly cloudy, chance of rain"? 

An avalanche forecast is a moderately complicated weighted integral of past, present, and near future weather.  For the lowland forecast, 'mostly cloudy, chance of rain' is accurate; they're developing the capacity to say, "Cloudy 'till 10 am, sunbreak 'till 11:30, then cloudy again. Drizzle arriving at 3:30, turning to light rain at 4, then back to drizzle. Probably shouldn't have a barbecue."  but it's hard to provide such local specificity in a broad forecast, and confidence in timing and precip amounts is often limited.  So, we get the broadbrush forecast of 'mostly cloudy, chance of rain'.  It's accurate, and fairly precise.

Switching to a lower-resolution rating system for weather, say, "Bomber, Alright, Bad, Horrible", only means that the forecaster gets to anguish over the difference between Alright and Bad a lot of the time, and there are a lot of complaints when it happens to rain on an Alright day or if it happens to be sunny on a Bad day. Having a fifth option, say, "Middling", lets me know that I should bring a raincoat, but that it might be nice. If I want to know more, I'll check out the forecast discussion , where the forecasters can give me hints about what they think might happen.


The more I think about it, the more I like the notion of an avalanche forecast as an aggregation of weather past, present, and future. At its core, it's a complicated weather forecast; can't blame the weatherman for accurately reporting what's going to happen.

The more I think about it, the more I like the notion of an avalanche forecast as an aggregation of weather past, present, and future. At its core, it's a complicated weather forecast; can't blame the weatherman for accurately reporting what's going to happen.

agree...

I don’t think the rating system is broken. Considerable is not difficult to understand and if you think you can relax just because the day is rated moderate or low then its just a matter of time…
This is not the way to look at the rating system. I don’t mean to be harsh, but anyone who dies based on the rating alone is not understanding how to use it in the first place, and would not have mattered how the rating scheme is structured. Everything I have read about incidents involving experienced people indicates a breakdown in group dynamics affecting risk assessment in the field. It only makes sense that the majority of incidents happen in the middle of the rating scale, changing its structure will not change that. People really need to separate the rating from the mitigation and task at hand especially in large groups… if your not certain the slope will not slide the rating (and your complacency with considerable) should not be part of the decision. The rating has NOTHING to do with the stability of the aspect your exposed to in the field…



The important thing to ask yourself when you do not find instability on a considerable day is what were the decisions that affected your outcome? Maybe if you ask that, you will quickly lose your complacency with the “considerable” rating!

Hm. Is it bothersome that the lowland weather forecast is, through most of the winter, "mostly cloudy, chance of rain"? 

An avalanche forecast is a moderately complicated weighted integral of past, present, and near future weather.  For the lowland forecast, 'mostly cloudy, chance of rain' is accurate; they're developing the capacity to say, "Cloudy 'till 10 am, sunbreak 'till 11:30, then cloudy again. Drizzle arriving at 3:30, turning to light rain at 4, then back to drizzle. Probably shouldn't have a barbecue."  but it's hard to provide such local specificity in a broad forecast, and confidence in timing and precip amounts is often limited.  So, we get the broadbrush forecast of 'mostly cloudy, chance of rain'.  It's accurate, and fairly precise.

As the middle rating in the system, I would say that a better comparison in the eyes of those who use an "at a glance" rating system such as from NWAC, would be the ubiquitous "partially cloudy, chance of showers" broadbrush forecast which represents the middle of the road rating we get more than anything around  the NW.  On most days, is there finer grained meteorological data available to make decisions?  Certainly, but most people don't know how, or don't take the time to do so.  No one in the NW ever canceled a BBQ based on a forecast of "partially cloudy, chance of showers".  Instead, you bring a raincoat, tarps, and have a backup plan.  Sometimes you get dumped on, other times it is sunny.  Either way, everyone laughs at how little the weather man or woman knows.

Avy danger and backcountry travel is obviously more serious than a BBQ at Golden Gardens, and considerations made should reflect this.  As has been pointed out, the "considerable" or middle category provides the greatest opportunity to introduce the human factors as discussed in Temper's book.

Most of the comments in defense of the "considerable" rating seem to agree that there is a wide range of variability in what this could mean at any given location, and that a detailed review of available online data, and observable conditions on location are what the backcountry traveler requires to make the best decisions.  While true, this ignores the whole reasoning for creating a traffic light system to begin with, which is that it aims to reach different users who will not, or do not know how to interpret the more detailed information that may be available by simplifying everything.

By virtue of even reading this bulletin board, readers are likely to have some level of avalanche training if not being among the most expert in the region.  It is worth remembering that avalanche training experts are not the target audience for the NWAC traffic light rating system.

Disagree, Does a green light mean it’s safe to enter the intersection? The rating system is not a go-no go gage and should be taught separate from the risk mitigation at hand.

"what is the effectiveness of a rating that constitutes a large portion of the ratings listed during days in areas where avi fatalities occur?"

It's very effective. There are lots of days where considerable does, generally, describe the day's avy risk. Changing the terms will not decrease the number of days with considerable risk. Reducing the rating resolution will not help folks who fundamentally base their decisions on a forecast.

NWAC isn't an oracle. There is simply no general answer to "is it safe out there?"

I think my frustration is with this rating change tack to reducing avy fatalities. There very well may be a better rating system possible. I doubt it would save lives. Certainly not the recent sad losses we've had in WA and probably not those in CO.

There is a risk in leading the general public to a conclusion that the NWAC ratings could have been better and therefore a forecast tweak will save lives. Its a passive conclusion that doesn't require any change in behavior. The better takeaway is that people should be awed and appropriately fearful of nature and our snowpack.

The discussions around group dynamics and decision making are much more likely to bear fruit. Our energy is better spent there.

Chuck, some "criers" have loads of experience in a variety of snowpacks.  I simply ask the question, "what is the effectiveness of a rating that constitutes a large portion of the ratings listed during days in areas where avi fatalities occur?"

Although it is true most avalanche accidents happen in Considerable hazard I think one needs to look at the reasons behind the statistics. In Moderate hazard forecasters would tell you that they expect few reports of incidents, none most commonly on a Moderate day. So people don't get caught very often. I really only worry about Moderate hazard if there is a generally stable snowpack but one that has historically had bad layers, near wind-loaded features usually above treeline, or in warm weather. In High hazard there is enough public information out there (backcountry travel is not recommended) that few venture out. So there aren't as many accidents. In High hazard with an expectation of good skiing to make it worthwhile, I'll usually ski in safe forests. But in Considerable hazard people do venture out. Forecasters would tell you that they expect to hear of some incidents and there is still significant hazard. So, it is not surprising that there are more accidents in Considerable hazard. The word "consider" is the root of Considerable.

But much more important than the level of the hazard is the text describing the situation from an avalanche perspective. It is here that you'll appreciate recent reports of avalanches or highly unstable snow. It is in the text (and the supporting telemetry) that you'll appreciate the significance of recent wind-loading, and of particularly troublesome weak layers like icy crusts, facets, and surface hoar. The text is the key beginning element to arm yourself with in discussing with your friends an appropriate choice of a tour on a particular day.

Avi fatalities in the region covered by NWAC are far too rare to glean much, if any, statistically valid causal relationship between the system's nomenclature and the decisions made by the victims.  Unless we can figure out a way to debrief these victims, this isn't going to change.    

Both recent victims were highly educated and had spent a lot of time in the backcountry.   Was 'considerable' inherently confusing to them?  I'm not going to speculate other than to say that perceived ambiguity of the rating probably wasn't much of a factor in the eventual tragic outcomes here.   

One might argue that, whatever the nomenclature, accidents will tend to happen in the zone between moderate and high - whatever you call it.  Does that speak to the need to eliminate this essential category? 

No.

One might also conclude that, because avi accidents are so rare, the system works very well to provide one valuable piece of data in a decisions that should also include local observation, a consideration of weather history, and current weather.   Probably not supportable by any data - just another way of looking at it.

Like traffic accidents, until we have fully automated skis that veto the rider's desire to venture into harms way, avi fatalities will continue to happen, regardless of how sophisticated or dumbed down the warning system is.

   

My thought is that between the normalization of risk (chances taken without consequence that alter the risk perception) among many backcountry skiers and increasingly crowded and more socialized places to ski, "considerable" basically defaults to GO and make sure your buddies are nearby. 

That is a problem with decision-making of those many skiers, and not of the avy forecast system. The folks who I often ski with view Considerable a bit differently - more along the lines of "we'd better have a safe route up and do repeated stability evaluation as we go, and we should tend toward more cautious slope choices for our descent - e.g. not big long slopes that could slide very long way entraining lots of snow but rather slopes that are broken up by benches or mellower stretches, and also typically tree skiing where the new snow depth will be a bit less and the nature of the snow surface typically a bit different" (though I've seen a partner trigger a decent-sized pocket slab in deep forest on a considerable day - had we been on a more continuously steep slope such a slide would likely have been larger). The exact nature of these decisions depend a fair bit on how much snow has fallen over the potential sliding layers. There are some considerable days when we just say "let's ski the lifts" or otherwise occupy ourselves due to both the risk and the potential "wallow factor" that would lead us to either be skiing figure 11s or going onto steeper slopes than we'd like to tackle given the mix of the rating and the depth of potential slides.

I recall the older system that lacked this rating, and I've found the newer system to be an improvement - a bit more precision about what the forecasters are thinking. Looking at fatality stats since the change is not super informative, given all the other confounding factors (increase in backcountry skier population, improvements in ski shape which makes skiing deeper fresher snow more rewarding instead of painfully wallowy, etc.).

However, I think the NYT article about the Tunnel Creek incident mentioned something along the lines of a "bigger further faster" attitude that was on the increase. Perhaps this is in play as people say "GO" when they read "Considerable?" Does anyone really think that removing a step from the rating scale is going to change this dynamic and reduce risk level among this cohort?? Tony - I'd submit that if you remove this rating level, you'll just find that the majority of the fatalities will be occurring at some other level that contains the conditions most often seen on days currently called Considerable.

As for folks who need binary traffic lights due to lack of basic avy education, I think their light should always be "red" when there is more than a small bit of snow on the ground.

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As for folks who need binary traffic lights due to lack of basic avy education, I think their light should always be "red" when there is more than a small bit of snow on the ground.

Nicely said; that seems to go for so many activities in life.

I have done a little research, but can not fully substantiate the following postulation "if recommendations in the avalanche bulletin were followed there would be few, maybe no avalanche fatalities (in PNW)". Learning to read the bulletin (know what the words mean) and follow the recommended terrain choices should be of high priority to us. Furthermore we should learn to watch for (usually easily recognizable) signs of snow instability. It is not rocket science, but maybe it should be, as we really try to overcomplicate our decisions at times, so much as we end up not seeing the forest for the trees.

This is how I think:
Low danger level - i dont spent much time thinking about the snowpack
Moderate - i start thinking about what avalanche problem is the concern and how can i avoid it in the terrain (surface hoar down 50 cm in specific terrain vs point releases in 15 cm storm snow provides me different feelings when i think about likelihood vs consequences)
Considerable - i spend more time analyzing the terrain and making sure that i can avoid the forecasted problem(s). i increase my margins of safety and really try to listen to my certainty and uncertainty. The hairs on the back of my neck are standing up now.
High and Extreme - some times fun to go out on days like these if able to manage the hazard by absolutely avoiding the terrain in which it is present.

To me the rating of Considerable and the accompanying text is very descriptive. "You face a considerable risk of getting hurt if you enter avalanche terrain". Sounds pretty clear to me. However, having followed the research on human factors and kept a little track of the statistics, there seems to be something missing........... some communication that does not come across. Or is it that it is ignored?

Chances of dying or getting seriously hurt in an avalanche are very low if we let simple tools guide our terrain choices (bulletin/observations available to the naked eye). I fail to understand completely how we think we are above making it simple..........

Anyway, i like the 5 part system and think that considerable is a suitable descriptor to me.

I appreciate all the replies and agree with most of the points as they concur with my experiences in the PNW. I previously spent a number of years in Colorado and still have a conservative clinometer built into my brain and usually receive well-intentioned ribbing for my tentative approach to places commonly skied here.

Cheers!

The considerable rating becomes more useful the more one uses the incredible device located behind the eyes and between the ears.

The considerable rating becomes more useful the more one uses the incredible device located behind the eyes and between the ears.

Do they sell those at REI?

The comments that I really agree are the folks who regard the considerable rating as time to truly evaluate EVERYTHING.

I do a lot of solo touring with my dog, and when things hit considerable it all changes for me in terms of where I will go and what I will do. So many times I have backed down on plans.

This winter I have commented a number of times that it is all about coming back for another day. No one day of good powder skiing will ever change that for me and make me risk my life.

I have skied literally 100s of pow days in my life and feel blessed. If I never have another I would surely be sad but always know that I have experienced the best.

Considerable is serious

This winter I skied an exposed line this on a considerable day, it was solid. The next day NWAC reported avalanches at a location adjacent to the ski resort ~3 miles away from ours on the same day we skied…  it was certainly “considerable” over there one could argue the rating should have been high!

On a lighter note when once I was getting scolded by my friend for me not checking the forecast we got a good laugh when I jokingly replied what’s the big deal, how is that going to change our plans when it’s always considerable anyways?

Can't help wondering what kind of a hueristic trap this may form in your mind...

Up until this week I had a problem with "considerable". I've already expressed my concerns with it so I won't get into why I thought it was a weak rating. Earlier this week I got a change to listen to a presentation by Scott Schell and afterwards chat with him a bit about my concerns with considerable along with a few other things. He gave the best explanation of each level of warning that I have had so far and I've been through 3 consecutive years of AIARE L1 courses plus a previous similar course 14 years ago and lots of time reading the NWAC site.

His explanation of considerable and high was that the avalanche problem/concern and characteristics are usually very similar but the spatial distribution of likely start zones is different. On a considerable day avalanches are likely to start from more obvious features and on a high day a similar avalanche is likely to start from less obvious features.

I also appreciate the size prediction more now too with small being a slide up to D1.5 and large being D2. No need for medium if the line is drawn at the likelihood of injury.

I have to admit that I really like the development of the new NWAC site now that I've learned a bit more about it and have spent more time looking around. A lot of information that I was wanting is there but sometimes it's not so obvious.

I still have my concerns about complacency developing from seeing the same bulletin frequently without seeing activity in the field. I know that information is included in the snowpack discussions related to recent activity but I think it would be helpful to really push the connection between the rating and what's going on by having a more prominent link to pictures of recent activity along with what the bulletin/forecast was for that day.